Regional difference in the characteristics of dust event in East Asia

摘要

The regional difference in the characteristics of dust event in East Asia was investigated by use of surface meteorological data from March 1988 to May 2004. Referring to the topography and land cover type, East Asia was divided into 11 regions. Among these regions, dust outbreaks frequently occur in Gobi Desert, the western part of Loess Plateau, and Taklimakan Desert whose land cover types are Bare Desert and Semi Desert Shrubs (i.e., desert). Although the result of frequent dust outbreaks is common among these regions, the frequency of floating dusts differs greatly. Floating dusts are frequently observed in Taklimakan Desert. On the other hand, floating dusts are seldom observed in Gobi Desert and Loess Plateau. In these regions, although dusts are produced by synoptic disturbances, they are immediately swept away by these synoptic disturbances. We clarified the regional difference of the relation among dust outbreak, surface wind, and land surface condition by analyzing the correlation between dust outbreak frequency and strong wind frequency when the threshold velocity is set to be a constant, 6.5 m/sec. From this analysis, we found that the surface wind primarily controls dust outbreaks in desert regions in March and April. On the other hand, land surface conditions primarily control dust outbreaks in Grassland. When we consider the effect of snow cover, remarkable effects of snow cover are found in Inner Mongolia and Hexi Corridor in March, and Northern Mongolia in April.